1. Field of the Invention
The present invention relates to an electric charging system and an electric vehicle, and, in particular, to a technology for determining a power supply state between a charger and an electric vehicle.
2. Description of the Related Art
In recent years, electric vehicles that are equipped with an electric motor for propulsion have been under development. When an electric storage device such as a battery that is installed at the electric vehicle is charged, a charging cable extending from an electric charger is connected to a charging port of the electric vehicle (see, for example, Japanese Unexamined Patent Application Publication No. 2009-83670). Furthermore, in the field of hybrid electric vehicles that are equipped with an engine and an electric motor for propulsion, a hybrid electric vehicle of the so-called plug-in system, in which an electric storage device is charged with an electric charger, is under development.
However, since power supplied from the electric charger to the electric vehicle has a high voltage and a high capacity, it is necessary to monitor the insulation failure and disconnection of the charging cable in order to prevent current leak and ensure safety during charging. A method of comparing the voltage supplied from the electric charger with the voltage received by the electric vehicle and a method of comparing the current supplied from the electric charger with the current received by the electric vehicle are known as methods for monitoring insulation failure and the like. When there is a large difference between the supplied and received voltages or between the supplied and received current, it can be assumed that the power flow is occurring to other than the electric vehicle and it can be determined that an insulation failure or the like has occurred.
When the insulation failure or the like is thus detected, voltage data or current data outputted from the voltage sensor or current sensor are used, but when those data are used the effect of noise is typically eliminated by performing a filter processing such as a moving average processing. However, since a time lag appears in voltage data or current data after the filter processing, simple comparison of voltage data at the electric charger side and the electric vehicle side causes erroneous determination of insulation failure and the like. Thus, when a difference in lag time occurs between the electric charger side and the electric vehicle side and the data from the electric charger side and the electric vehicle side are not synchronized, there is a large separation between the two groups of data even when no insulation failure has occurred, and there is no separation between the two groups of data even when an insulation failure has occurred.